Production of tetrasila-adamantane compounds

ABSTRACT

TETRASILA-ADAMANTANE COMPOUNDS ARE PRODUCED BY THE HIGH TEMPERATURE (400*C.) AND HIGH PRESSURE (1500 P.S.I.) REACTION OF METHYLHALOSILANES IN THE PRESENCE OF ALUMINUM CHLORIDE OR ALUMINUM BROMIDE AS A CATALYST AND SILICON OR ALUMINUM METALS AS AN ACID ACCEPTOR. THE COMPOUNDS ARE USEFUL AS MOSQUITO REPELLENTS.

United States Patent 3,631,197 PRODUCTION OF TETRASlLA-ADAMANTANE COMPOUNDS Jerome M. Klosowski, Bay City, and Arthur J. Barry, Midland, Mich., assiguors to Dow Corning Corporation, Midland, Mich. No Drawing. Filed May 18, 1970, Ser. No. 38,498 Int. Cl. C07d 103/02 U.S. Cl. 260-4482 E 8 Claims ABSTRACT OF THE DISCLOSURE Tetrasila-adamantane compounds are produced by the high temperature (400 C.) and high pressure (1500 p.s.i.) reaction of methylhalosilanes in the presence of aluminum chloride or aluminum bromide as a catalyst and silicon or aluminum metal as an acid acceptor. The compounds are useful as mosquito repellents.

This invention relates to an improved method of producing tetrasila-adamantane compounds.

Tetrasila-adamantane compounds can be represented by the structural formula on, on, on,

Si oa -saon, on,

This cage structure, Whose four bridgehead silicon valences are tetrahedrally arranged, forms a tetravalent nucleus which can be conveniently represented by the symbol Ad. The methyl-substituted tetrasila-adamantane, (CH Ad, has been produced by the pyrolysis of tetramethylsilane at 650 C.see Fritz et al., Carbosilanes, Advances in Inorganic and Radiochemistry, vol. 7, page 349, Academic Press (1965). The chlorinated compound, AdCl was obtained in very low yield from the high temperature (500 C.) reaction of tetrachlorosilane and trimethylchlorosilane in the presence of aluminum chloride as reported in JACS, 83, 3345 (1961).

By practice of the present invention, wherein silicon or aluminum is used as an acid acceptor in the aluminum halide catalyzed reaction of halosilanes, the yield of tetrasila-adamantane compounds is greatly increased.

It is an object of the invention to provide an improved method of producing tetrasila-adamantane compounds.

In accordance with the invention, tetrasila-adamantane compounds of the general formula R Ad, in which each R is independently selected from the group consisting of the chlorine atom, the bromine atom and the methyl radical, are obtained by reacting (CH ),,SiX in which X is a chlorine or bromine atom and n is an integer having a value of from 1 to 4, in the presence of (1) a catalyst selected from the group consisting of aluminum chloride,

ice

aluminum bromide and mixtures thereof, and (2) a metallic acid acceptor selected from the group consisting of silicon, aluminum and mixtures thereof, the reaction being efiected at a temperature of at least 300 C. and a pressure in the range of 1000 to 2500 p.s.i.

The starting materials used in the process of the invention iIlClHdC (CH3)2SiBI'2, CH SiBr CH SiCl (CH SiBr, (CH Si; and mixtures of such materials. These compounds are well-known and most are commercially available.

The catalyst, aluminum chloride or aluminum bromide, is present in a catalytic amount, generally in the range of about 2.5 to 15 percent by weight, based on the weight of reactants. The silicon or aluminum metals act as acid scavengers during the reaction and are necessary to obtain any appreciable yield of tetrasila-adamantane from the reaction. These metallic acid acceptors are effective in amounts as low as 2.5 percent by weight based on the weight reactants, while amounts greater than 50 weight percent do not give any additional benefit.

The reaction is conducted at a temperature of about 300 C. or greater. At temperatures below 200 C., the rate of reaction is so slow as to be impractical. Temperatures above 600 C. may result in thermal degregration of the product. The optimum temperature of reaction is in the range of from about 350-450 C. The reaction is usually complete in from 2 to 8 hours.

The product of the reaction is a mixture of variously substituted tetrasila-adamantanes, including CH AdCl CH AdBr (CH AdCl (CH AdBr (CH AdCl, (CH AdBr CH AdClBr (CH AdBrCl, AdBr and AdCl Pure species of the products can be isolated by sublimation if desired.

The product species having at least one methyl substituent have been determined to be useful as mosquito repellents. The tetrahalo-tetrasila-a'damantanes can be reacted with tetramethylsilane in the presence of aluminum chloride to yield the useful methyl-substituted tetrasilaadamantanes. This ligand redistribution reaction proceeds Well at atmospheric pressure and relatively low temperatures, for example 60 C. Exemplary of such a redistribution is the reaction shown below:

A1013 (CH )4Si AdCh (CH AdCl other species 60C. 10 hrs.

The following examples are illustrative, but not limiting, of the invention which is delineated in the claims.

EXAMPLE 1 A 2.4 liter steel pressure vessel was charged with 651 grams of trimethylchlorosilane, 17.5 grams of aluminum and 33 grams of aluminum chloride, The pressure vessel was then heated to 390398 C. for 4 /2 hours while being rolled to agitate the contents which reached a peak pressure of about 2200 p.s.i. Upon cooling to room temperature, a residual pressure of 530 p.s.i. was retained. Low boiling product, principally methane, was distilled from the pressure vessel at atmospheric pressure to a vapor temperature of C. at 5-10 mm. Hg. Upon sublimation, the remaining product yielded (CH AdCl. (CH AdCl and CH AdCl each of which were identified by g.1.c. analysis and mass spectral data.

EXAMPLE 2 4 That which is claimed is: 1. A method of producing tetrasila-adamantanes of the general formula 5 A mixture of 651 grams of trimethylchlorosilane, 17.5 grams of silicon, 17.5 grams of aluminum and 3.3 grams of aluminum chloride were reacted in the manner set forth in Example 1 for 3.8 hours at 390398 C. After cooling to room temperature, residual pressure in the vessel was 1 540 p.s.i. The reaction mixture was distilled to give 5.45 grams of (CH AdCl and 22.33 grams of CH AdCl each of which were identified by g.l.c. analysis and mass spectral data.

EXAMPLE 3 A mixture of 684 grams of trimethylchlorosilane, 17.5 in which each R is independently selected from the group gr m f silicon and 3 grams f l minum chloride were consisting of the chlorine atom, the bromine atom and the reacted at from 390398 C. at a pressure of about 1000 methyl radical; said method comprising reacting p.s.i. for 6 hours. The final pressure was 2330 p.s.i. After (CH SIX cooling to room temperature, a residual pressure of 430 3 n p.s.i. was retained. The reaction mixture was distilled and n Which X is a Chlorine bromine atom, n is a integer sublimed to obtain 0.3 gram of (CH AdCl, 6.3 grams having a Value Of from 1 t0 in the Presence of a of (CH AdCl and 14.7 grams of (CH )AdC1 catalyst selected from the group consisting of aluminum EXAMPLE 4 chloride, aluminum bromide and m1xtures thereof and (2) a metallic acid acceptor selected from the group consisting A mixture of 12 moles of dimethyldichlorosilane, one of silicon, aluminum, and mixtures thereof, at a temperamole of silicon, one mole of aluminum and 10 weight perture of at least about 300 C. and a pressure in the range cent, based on the weight of the reactant, of aluminum of 1000 to 2500 p.s.i. chloride were reacted in the previously-described pressure 2. The method of claim 1 wherein said catalyst is vessel for 10 hours at 395 C. The final pressure was 1450 aluminum chloride bromide. p.s.i. The principal product was AdCl 3. The method of claim 1 wherein said catalyst is In a similar experiment tetramethylsilane was reacted in aluminum bromide. the presence of silicon, aluminum and aluminum chloride 4. The method of claim 1 wherein said acid acceptor for 6.5 hours, attaining a final pressure of 2310 p.s.i. to is aluminumyield (CH Ad and (CH AdCl. 5. The method of claim 1 wherein said acid acceptor is silicon. EXAMPLE 5 6. The method of claim 1 wherein said reactant is tri- The methyl-substituted tetrasila-adamantanes produced methylchlorosilaneby the method of the invention were determined to be The method of claim 1 wherein Said catalyst mosquito repellents by means of the following procedure: is Present in an amount in the range of about to 15 2" x 2" shaved areas of the skin on the testers forearms Pefee!1t by Weight based on the Weight of reactants and and backs of hands were exposed for a given period of metallic acid acceptor (2) is present in an amount time to approximately 500 mosquitoes of the species In the rallge of about to 50 Pereent y Weight, based Aedes aegypti in a 12" x 12" x 12" cage. The mosquitoes 011 the Welght of the had be d i d warm bl for three days The mosqui 8. The method of claim 7 wherein said temperature is toes were excited and put to flight before the hand or arm m the range of about 350 to was put into the cage. The arm or hand was masked with polyethylene sheet material except for the test area. As a References Cited 2:823:58 ttlillee gntriatetifslrindwas exgogetd to the mosgu- UNITED STATES PATENTS urn er an mgs an 1 es were recor e The methyl-substituted tetrasila-adamantane compositions 334288O 9/1967 Reinhardt 260 44820 X were then applied to the control area and it was again exposed to the same mosquitoes for at least a compara- TOBIAS LEVOW Primary Exammer ble period of time; the number of landings and bites be- R SHAVER, Assistant Examine! ing recorded. No test area was used for more than one repellent. Exemplary data obtained by this procedure is given below: 260-448.2 D; 424-184, Digest 10 Amount appl 1 to 2" x 2" Compound area (grams) Time exposed Landings Bites iiil oasxajiiiiij113111231123: 28?: ifiiiiigo iiisizoiigr" 2 24 3 Crggoilidaf None 30 sec 11 11 40 errata-oat; 30sec s a 

